import SwiftUI

struct ExpertView: View {
    @ObservedObject var connectionService: ConnectionService
    @StateObject private var viewModel: ExpertViewModel
    @AppStorage("appLanguage") private var appLanguage: String = "de"
    @AppStorage(AppPreferences.colorThemeKey) private var colorThemeRaw: String = ColorTheme.standard.rawValue
    private var colorTheme: ColorTheme { ColorTheme(rawValue: colorThemeRaw) ?? .standard }
    /// A category's presence in this set means "collapsed". Starts with every category
    /// collapsed (Nutzerwunsch: "standardmäßig sollten beim Öffnen des Experte-Tab alle
    /// Sektion zugeklappt sein") — click a header to fold its menu list open again.
    @State private var collapsedCategories: Set<RouterOSMenuCategory> = Set(RouterOSMenuCategory.allCases)
    @State private var isCustomPathExpanded = false

    init(connectionService: ConnectionService) {
        self.connectionService = connectionService
        _viewModel = StateObject(wrappedValue: ExpertViewModel(connectionService: connectionService))
    }

    var body: some View {
        Group {
            if connectionService.credentials == nil {
                ContentUnavailableView(
                    LocalizedStringKey(L10n.t("Nicht verbunden", appLanguage)),
                    systemImage: "network.slash",
                    description: Text(L10n.t("Verbinde dich zuerst im Tab \"Verbinden\" mit deinem Router.", appLanguage))
                )
            } else {
                NavigationSplitView {
                    List {
                        ForEach(RouterOSMenuCategory.allCases) { category in
                            let schemas = RouterOSSchemaCatalog.schemas(in: category)
                            if !schemas.isEmpty {
                                let isExpanded = !collapsedCategories.contains(category)
                                Section {
                                    if isExpanded {
                                        ForEach(schemas) { schema in
                                            let isSelected = viewModel.selectedSchema?.menuPath == schema.menuPath
                                            Button {
                                                viewModel.open(schema)
                                            } label: {
                                                Text(L10n.t(schema.displayName, appLanguage))
                                                    .frame(maxWidth: .infinity, alignment: .leading)
                                                    .padding(.vertical, 4)
                                                    .padding(.horizontal, 6)
                                                    .background(
                                                        RoundedRectangle(cornerRadius: 6)
                                                            .fill(isSelected ? Color.blue.opacity(0.25) : Color.clear)
                                                    )
                                                    .contentShape(Rectangle())
                                            }
                                            .buttonStyle(.plain)
                                        }
                                    }
                                } header: {
                                    sectionHeader(L10n.t(category.rawValue, appLanguage), isExpanded: isExpanded, categoryColor: colorTheme.color(for: category)) {
                                        if isExpanded {
                                            collapsedCategories.insert(category)
                                        } else {
                                            collapsedCategories.remove(category)
                                        }
                                    }
                                }
                            }
                        }

                        Section {
                            if isCustomPathExpanded {
                                Text(L10n.t("Jeder RouterOS-Menüpfad ist erreichbar, auch wenn er oben nicht gelistet ist — die Felder erscheinen dann generisch (Schlüssel/Wert), ohne kuratierte Erklärung.", appLanguage))
                                    .appFont(.caption)
                                    .foregroundStyle(.secondary)
                                TextField(L10n.t("Menüpfad, z.B. /ip firewall filter", appLanguage), text: $viewModel.customMenuPath)
                                    .help(L10n.t("Der RouterOS-CLI-Pfad, z.B. \"/interface wireguard\" oder \"/routing ospf instance\".", appLanguage))
                                TextField(L10n.t("REST-Pfad, z.B. ip/firewall/filter", appLanguage), text: $viewModel.customRestPath)
                                    .help(L10n.t("Derselbe Pfad in REST-API-Schreibweise: führende \"/\" weg, Leerzeichen zu \"/\".", appLanguage))
                                Button(L10n.t("Öffnen", appLanguage)) { viewModel.openCustomPath() }
                                    .disabled(viewModel.customMenuPath.isEmpty || viewModel.customRestPath.isEmpty)
                            }
                        } header: {
                            sectionHeader(L10n.t("Eigener Menüpfad", appLanguage), isExpanded: isCustomPathExpanded) {
                                isCustomPathExpanded.toggle()
                            }
                        }
                    }
                    .listStyle(.sidebar)
                    .navigationTitle(LocalizedStringKey(L10n.t("Experte", appLanguage)))
.toolbar { ToolbarItem { ManualHelpButton(anchor: ManualAnchor.tabExpert) } }
                } detail: {
                    if let schema = viewModel.selectedSchema {
                        ExpertMenuDetailView(
                            viewModel: viewModel,
                            schema: schema
                        )
                    } else {
                        ContentUnavailableView(
                            LocalizedStringKey(L10n.t("Kein Menü ausgewählt", appLanguage)),
                            systemImage: "list.bullet.rectangle",
                            description: Text(L10n.t("Wähle links einen RouterOS-Bereich aus.", appLanguage))
                        )
                    }
                }
            }
        }
    }

    /// Custom Section header — plain `Section("title")` rendered as macOS' default tiny
    /// gray-caps sidebar label, too easy to miss when scanning nine menu categories (Nutzerwunsch:
    /// "müssen prominenter sein und eingefärbt"). `.textCase(nil)` is required here, or macOS
    /// forces its own uppercase-small-caps styling back on top of this custom view regardless of
    /// the font/background set below. `Color.accentColor` (not a fixed RGB value) so the tint
    /// stays visible and correctly contrasted in both light and dark mode automatically.
    ///
    /// The chevron is drawn explicitly here rather than relying on `Section(isExpanded:)`'s
    /// built-in disclosure triangle — that one is macOS sidebar-standard hover-only (matches
    /// Finder), which the user explicitly didn't want ("der Pfeil sollte immer zu sehen sein und
    /// nicht erst beim Hovern"). The whole header is a plain `Button` toggling `onToggle`, with
    /// the section's own content shown/hidden by the caller via a plain `if isExpanded` instead
    /// of the `Section(isExpanded:)` API, since that API owns its own (hover-only) chevron.
    private func sectionHeader(_ title: String, isExpanded: Bool, categoryColor: Color? = nil, onToggle: @escaping () -> Void) -> some View {
        Button(action: onToggle) {
            HStack(spacing: 6) {
                Image(systemName: "chevron.right")
                    .appFont(.caption, bold: true)
                    .foregroundStyle(.secondary)
                    .rotationEffect(.degrees(isExpanded ? 90 : 0))
                if let categoryColor {
                    Circle().fill(categoryColor).frame(width: 8, height: 8)
                }
                Text(title)
                    .appFont(.title3, bold: true)
                    .foregroundStyle(.primary)
            }
            .padding(.vertical, 6)
            .padding(.horizontal, 8)
            .frame(maxWidth: .infinity, alignment: .leading)
            .background(RoundedRectangle(cornerRadius: 6).fill(Color.accentColor.opacity(0.18)))
            .contentShape(Rectangle())
        }
        .buttonStyle(.plain)
        .textCase(nil)
    }
}

#Preview {
    ExpertView(connectionService: ConnectionService())
}